Process for equipping a kitchenware object with an anti-adhesion coating

ABSTRACT

The invention relates to a process for equipping a kitchenware object, for example a pan, a pot, roasters or the like, comprising metal, for example aluminum, an aluminum alloy, magnesium or a magnesium alloy, with an anti-adhesion coating in the stressed surface regions, for example, on the inside, in which onto the metal surface of the object, for example after roughening, a mechanically-resistant layer, such as a mechanically-resistant anodization layer or similar mechanically-resistant layer is provided, and subsequently the stressed surface regions are provided with the anti-adhesion layer, wherein, before providing the mechanically-resistant layer, a durable surface layer is applied onto the surface regions, not to be provided with the coating system (mechanically-resistant layer or the like with or without anti-adhesion layer), of the object.

The invention relates to a process for equipping a kitchenware object,for example a pan, a pot or the like, comprising metal, for examplealuminum, an aluminum alloy, magnesium or a magnesium alloy and/orcopper alloy, with an anti-adhesion coating system in the stressedsurface regions, for example on the inside, which, for example afterroughening, comprises a layer of a mechanically-resistant material suchas a mechanically-resistant anodization layer or similar anodizationlayer, and an anti-adhesion layer, comprising for example a fluorocarbonresin, such as polytretafluoro [SIC] ethylene (PTFE), tetrafluoroethylene-hexafluoro propylene copolymer (FEP) or tetrafluoroethylene-ethylene copolymer (ETFE), thereby that before providing thelayer of mechanically-resistant material a surface layer is applied ontothe surface regions of the kitchenware object not to be provided withthe anti-adhesion coating system and subsequently the layer ofmechanically-resistant material is provided as an anodically-generatedconversion layer.

Such process is disclosed in GB-A-1 069 168. From it is evident that inthe production of a test pan initially in a partial region of the panbody a protection coat is provided while the exposed metal surfaceregion is provided with an intermediate oxide layer. For demonstrationpurposes, a partial region of this intermediate oxide layer again isprovided with a protection coat while the exposed intermediate oxidelayer is provided with an additional resin layer. After stripping offthe two protection coats, the different surface properties of theuntreated metal surface of the metal surface provided only with oneintermediate oxide layer and the smooth surface provided additionallywith a resin layer can be demonstrated.

According to a process disclosed in DE-B-1 546 934 and EP-A-0 424 072,kitchenware objects, such as pans, pots, roasters or the like, to someextent for increasing the scratch and wear resistance on their stressedinside, are provided with layers comprising mechanically-resistantmaterial in combination with anti-adhesion layers. In the case ofaluminum or magnesium alloys one possibility for applying a layercomprising mechanically-resistant material is the anodic oxidationaccording to DE-A-3 244 217. As a rule, the object to be anodized forthis purpose must be immersed in an acidic electrolyte bath whileelectrically connected and subsequently coated in the current flow witha conversion layer. In this process the entire object is provided on theinside as well as on the outside with the layer ofmechanically-resistant material.

In DE-A-3 806 699 is disclosed a process for coating household objects,in which the basic metal body is initially provided with a foundationadhesion layer, for example comprising nickel-aluminum orchromium-nickel. Onto this foundation adhesion layer is applied a layercomprising a mechanically-resistant material, for example comprisingaluminum oxide or a mixture of aluminum oxide and titanium oxide isapplied. Subsequently, the layer comprising the mechanically-resistantmaterial is provided with an anti-adhesion layer, for example based onpolytetrafluoro ethylene (PTFE). Each of the particular layers istherein sprayed onto the frying surface. In this process the opticalquality of the surface is said to be retained compared to prior knowncoating processes and that simultaneously the loadability of the layeris further increased.

DE-C-3 604 762 also discloses a process for coating kitchen containers,in which the surface is initially provided in the plasma sprayingprocess with a foundation adhesion layer comprising nickel-aluminum orchromium-nickel, subsequently during the plasma spraying process ontothe foundation adhesion layer a layer comprising amechanically-resistant material of aluminum oxide or aluminumoxide/titanium oxide is applied, furthermore onto the layer ofmechanically-resistant material [of: SIC] an anti-adhesion layer isapplied and lastly the anti-adhesion layer is burned in. The foundationadhesion layer comprises nickel-aluminum or chromium-nickel. Therequired layers are here also only sprayed onto the stressed surface,thus for example only [onto] the inner frying surface of a pan. In thisprocess, compared to previously known coating processes, the taskintended to be solved is that of attaining improved adhesion of theanti-adhesion layer on the surface of the kitchen container.

It is the task of the present invention to implement a process of theinitially cited type such that it can be carried out more economically.

This task is solved with the invention in a process of the initiallycited type essentially with the characteristics of claim 1. The processcosts are hereby reduced since for example in anodic oxidation, in spiteof the immersion of the kitchenware object in the electrolyte bath, onlya lesser area fraction is to be provided with the anodization layer. Thedurable surface layer serves not only for this saving but comprisessimultaneously specific functional properties; for, due to theappropriate material selection, it comprise a durable protection, cover,decoration and/or carrier layer for a further final cover layer. Apartfrom the fact that it can serve a decorative purpose, the surface layercan therein be designed for a special functional purpose, i.e. forimproving for example wear resistance, scratch resistance, corrosionprotection or thermal conductivity (on the bottom) independently of thecoating system to be provided on the inside of the kitchenware object.

As the surface layer are considered according to the invention primarilyanti-adhesion lacquer systems, enamelling and/or other acid-resistantorganic and/or inorganic coatings. If, for example,fluorocarbon-containing coating systems are used as surface layer, thesecan be applied as single, double or multiple layers, with or withoutintermediate drying/intermediate burning. The enamelling can also beapplied in single or multiple layers, with or without intermediatedrying/intermediate burning, in order to attain optimum acid resistance.The further acid-resistant organic or inorganic coatings can be based onthin- or thick-films with decorative and/or functional properties.

The surface layer is advantageously applied on the entire outside of thekitchenware object so that, due to a reduction to approximately one halfof the area fraction to be provided with the anodization layer, thecosts can be considerably reduced.

I claim:
 1. A process of equipping a metal cooking utensil having aninner surface coming into contact with the food to be cooked or friedwith an anti-adhesion coating system, which anti-adhesion coating systemcomprises an inner scratch and abrasion resistant layer and an outeranti-adhesion layer, which process consists essentially of firstlyapplying a durable surface layer onto a first surface region of themetal cooking utensil which is not to be provided with the anti-adhesioncoating system,subsequently immersing the metal cooking utensil in anacidic electrolytic bath to anodically generate the scratch and abrasionresistant layer onto a second surface region of the metal cookingutensil which includes the inner surface of the metal cooking utensiland excludes the first surface region of the metal cooking utensilprovided with the durable surface layer, and subsequently applying theanti-adhesion layer onto the scratch and abrasion resistant layer,wherein the durable surface layer is a protection layer or a cover layeror a decoration layer or a carrier layer for a further layer which isdurable during the life of the cooling utensil, provided that thedurable surface layer is not enamel.
 2. The process as claimed in claim1, wherein the durable surface layer is comprised of a lacquer coating,an acid resistant organic coating or an acid resistant inorganiccoating.
 3. The process as claimed in claim 1, wherein the durablesurface layer is applied onto the entire outside surface of the metalcooking utensil.
 4. The process as claimed in claim 2, wherein thedurable surface layer is applied onto the entire outside surface of themetal cooking utensil.